Filtration System

ABSTRACT

A filtration system and methods for using same are disclosed. The filtration system can include a frame, and a plurality of filters coupled to the frame and coupled to each other in series. A pump can provide a pressure differential that causes fluid to flow through the filters in series. The first filter can be provided as a pre-filter, and one or more additional filters can include pleated, calendared, micro-fiber filters. Another filter can be a percentage removal nano-filter that is adapted to remove sub-micron particles from the fluid. The nano-filter can include three pleated filter layers. Each pleated filter layer can be oriented approximately concentrically about a common longitudinal axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This claims the benefit of U.S. Provisional patent application Ser. No.61/220,375, filed Jun. 25, 2009, the disclosure of which is herebyincorporated by reference as if set forth in its entirety herein.

TECHNICAL FIELD

The present invention generally relates to filtration systems, and inparticular relates to a filter usable in a multi-unit filtration systemfor removing contaminants from a fluid.

BACKGROUND

Filters are widely used to remove contaminates from a fluid stream, gas,or liquid. For example, fluid that has been contaminated during anindustrial application can be passed through one or more filters of afiltration system that operates separately from the industrial process.The filtration system removes contaminating particles from thecontaminated fluid and outputs filtered fluid to the industrialapplication that has a lower level of contaminants than the contaminatedfluid.

Unfortunately, conventional filtration systems are expensive and do notreliably remove contaminating particles, particularly particles of smallsizes. As a result, the particles can amass within the industrialapplication, causing contamination, and/or clogging and ultimatelyinefficient downtime resulting from shutting down the application toperform maintenance.

It is desirable to provide a filtration system that can reliably andcost-effectively remove contaminants from a fluid associated with anindustrial process.

SUMMARY

Fluid filtration systems and methods are disclosed. A fluid filtrationsystem can include a frame, four filters coupled to the frame andcoupled to each other in series, and a pump coupled to a firstpre-filter. The four filters can include the first pre-filter. The fourfilters can include second and third pleated, calendared, micro-fiberfilters. The four filters can include a fourth percentage removalnano-filter that is adapted to remove sub-micron particles from thefluid. The nano-filter can include three pleated filter layers. Eachpleated filter layer can be oriented approximately concentrically abouta single longitudinal axis. The pump can be to create pressure in thefluid flowing through the four filters.

Each pleated filter layer can include electro-positive nanoaluminafibers grafted onto microglass structural fibers. The filtration systemcan further include a filter head having a mounting hub andcastellations located around the periphery of the mounting hub, a filterhead coupling each of the four filters to respective conduits. The fluidcan be usable in any desired industrial system, such as a printing pressor lithography fountain solution, a dairy or other agricultural farm, anelectroplating process, or any other system in which removal ofsub-micron sized contaminating particles is desired.

A method for filtering a fluid can include the steps of pumping a fluidfrom a processing environment into a first pre-filter, removing solidparticles greater than a minimum particle size of approximately 5-7microns from the fluid in the first pre-filter, pumping the fluid fromthe first pre-filter to a second pleated, calendared, micro-fiberfilter, removing solid particles greater than a minimum particle size ofapproximately 0.45-1 micron from the fluid in the second filter, pumpingthe fluid from the second filter to a third pleated, calendared,micro-fiber filter, removing solid particles greater than a minimumparticle size of approximately 0.2 microns from the fluid in the thirdfilter, pumping the fluid from the third filter to a fourth percentageremoval nano-filter, pumping the fluid through first, second, and thirdpleated filter layers located in the nano-filter, each filter layerbeing oriented approximately concentrically about a single longitudinalaxis, removing sub-micron size particles from the fluid in thenano-filter, and pumping the fluid from the nano-filter to theprocessing environment. All of the filter elements filter contaminants,such as contaminating particles, either through adsorption, absorption,and “catching.”

The step of pumping the fluid through first, second, and third pleatedfilter layers can include each pleated filter layer includingelectro-positive nanoalumina fibers grafted onto microglass structuralfibers. The fluid can be a printing press or lithography fountainsolution.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofa preferred embodiment, are better understood when read in conjunctionwith the appended diagrammatic drawings. The drawings show an embodimentthat is presently preferred. Thus, the invention is not limited to thespecific instrumentalities disclosed in the drawings. In the drawings:

FIG. 1 is a perspective view of a filtration system including aplurality of filters constructed and arranged in accordance with oneembodiment;

FIG. 2 is a perspective view of a filter illustrated in FIG. 1 connectedto a filter head;

FIG. 3A is a partial perspective view of a filter including a filterhousing and a filter cartridge;

FIG. 3B is a partial perspective view of the filter cartridgeillustrated in FIG. 3A;

FIG. 3C is a perspective view of the filter cartridge illustrated inFIG. 3A as fully assembled being inserted into the housing illustratedin FIG. 3A;

FIG. 3D is a perspective view of the filter cartridge illustrated inFIG. 3B fully inserted into the housing illustrated in FIG. 3B;

FIG. 4A is a sectional perspective view of the filter head illustratedin FIG. 2;

FIG. 4B is a sectional perspective view of a filter connected to thefilter head illustrated in FIG. 4A;

FIG. 5 is a perspective view of a multi-layer nanofilter suitable foruse in the filtration system illustrated in FIG. 1,

FIG. 6 is an enlarged view of a nanofilter layer of the nanofilterillustrated in FIG. 5, showing a pore defined between charged fibers ofthe nanofilter layer.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to FIG. 1, a filtration system 10 includes a plurality offilter assemblies including a first filter 12 a, a second filter 12 b, athird filter 12 c, a fourth filter 12 d, and a pump 13 connected inseries via corresponding conduits 17 and supported on a frame 11 or likesupport structure. Each filter 12 a-d is connected to a filter head oradapter 15 that connects the filter to the corresponding upstream anddownstream conduits 17. It should be appreciated that the terms“upstream” and “downstream” herein are used with respect to the flow offluid through the filtration system 10.

The filtration system 10 receives contaminated fluid at an inlet end 14from an industrial system 5. The industrial system 5 can provide anindustrial process, such as a chemical process, oil and gas process,water treatment process, printing process, electroplating processes,and/or any desirable process that utilizes a fluid in such a manner thatthe fluid can accumulate contaminating particles during operation. Theindustrial process can receive fluid from a basin or reservoir 6, whichcan also supply the contaminated fluid to the inlet end 14. In theillustrated embodiment, the pump 13 induces a pressure in the conduits17 that causes fluid to flow sequentially through the filters 12 a-d.The filters 12 a-d remove particles from the fluid to produce a cleanoutput fluid having a reduced quantity of particles with respect to thecontaminated input fluid.

The output fluid flows from the filtration system 10 into the reservoir6, which can be bifurcated into a first and second chamber that retainsthe contaminated and clean fluid, respectively. In this regard, theindustrial process of the industrial system 5 can input its fluid fromthe clean chamber, and output its used, contaminated fluid into thedirty chamber, while the filtration system 10 inputs contaminated fluidfrom the dirty chamber and outputs clean fluid into the clean chamber.It is appreciated that the flow of fluid through the industrial system 5and the filtration system 10 via the reservoir 6 is provided by way ofexample only, and numerous alternative configurations are envisioned.Accordingly, unless otherwise specified, the present invention is notintended to be limited to the described embodiment.

While the filters, collectively identified at 12, comprise four filtersthat are coupled together in series, it should be appreciated that thefiltration system 10 can alternatively include any desired number offilters, including, for example, 1, 2, 3, 5, 6, 8, 10, 12, or more,depending on the desired level of filtration, including the minimum sizeof particles to be removed, type of particles to be removed, and fluidflow rate through the filtration system 10.

In the illustrated embodiment, the filters 12 are configured to allow aprogressively smaller maximum particle size to pass through, as thefluid progresses sequentially from the first filter 12 a through to thefourth filter 12 d. All of the filters 12 function to filtercontaminants, such as contaminating particles, either throughadsorption, absorption, and “catching.” For example, the first filter 12a can be configured to remove particles having a largest dimensiongreater than or equal to approximately 7 microns, the second filter 12 bcan be configured to remove particles having a largest dimension greaterthan or equal to approximately 0.45 microns, the third filter 12 c canbe configured to remove particles having a largest dimension greaterthan or equal to approximately 0.2 microns to pass through, and thefourth filter 12 d can remove particles having a largest dimension lessthan 0.2 microns. Although filters 12 of specific particle size ratingsare discussed herein, filters 12 of any size rating can be used in thefiltration system 10, depending on the particular desired performancecharacteristics of the filtration system 10.

Referring now to FIG. 2, each filter 12 can be coupled to its associatedconduits 17 by its associated filter head 15. Each filter head 15includes an inlet end 60 and an outlet end 62 that is disposeddownstream of the inlet end 60. The inlet end 60 delivers contaminatedfluid to its associated filter, and the outlet end 62 receives filtered,or “clean” fluid from the associated filter, and provides a pathway forthe delivery of the fluid from the associated filter to a downstreamlocation.

Referring to FIGS. 3A-B, the general construction of the filters 12 a-dcan be described with reference to the first filter 12 a, unlessotherwise indicated. It should be appreciated that while oneconstruction is illustrated in detail, numerous filter constructions areenvisioned and intended to fall within the scope of the presentinvention unless otherwise indicated. In the illustrated embodiment, thefilter 12A can include an outer housing 40 and a cartridge 42 that isreceived by the outer housing 40. The cartridge 42 includes a porousouter annular shroud 44 and a porous inner annular post 46 that definesan internal cylindrical void 49. The filter 12A defines a housing void50 that is disposed between the outer housing 40 and the cartridge 42,and is in fluid communication with the filter head 15. The filter 12Adefines a cartridge receptacle 52 that is disposed between the annularshroud 44 and the inner post 46. The cartridge receptacle 52 can also beconfigured as an annulus depending on the geometric configuration of theshroud 44 and post 46. The filter media 48 can be disposed in thecartridge receptacle. The post 46 can be coupled to the filter head 15in the manner described below.

Both the shroud 44 and the post 46 can be formed from injection moldedplastic that is perforated to allow the fluid to flow through. Forinstance, the shroud 44 is illustrated as defining a plurality ofopenings 45 that are arranged in a plurality of circumferentially spacedaxial columns that extend therethrough and place the housing void 50 influid communication with the cartridge receptacle 52. The post 46likewise includes a plurality of openings 47 that are arranged incircumferentially spaced axial columns that extend therethrough andplace the cartridge receptacle 52 in fluid communication with thecylindrical void 49 of the post 46. The openings 47 can becircumferentially elongate as illustrated, or can assume any suitablealternative geometric configuration.

As shown in FIG. 3C, the filter cartridge 42 includes an upper end cap51 that closes the upper end of the shroud 44. The end cap 51 includes agenerally annular end cap body 53 that is sealed against the upper endof the shroud 44 either through a melting operation, an adhesiveoperation, or the like. Alternatively still, the end cap 51 can beintegral with the shroud 44. The end cap 51 defines an inner cylindricalcentral hub 55 that is aligned with the void 49 of the post 46. The hub55 can be sealed against, or constructed integrally with, the post 46,and can thus be considered an upper, or outer, end of the post 46.

The hub 55 can include a pair of grooves 28, each groove 28 beingadapted to accommodate insertion of a respective O-ring 29, which can beelastomeric or define any alternative material property as desired. TheO-rings 29 enhance the seal at the interface between the upper end ofthe hub 55 (or upper end of the post 46) and the inner surface of theassociated filter head 15. The double O-ring construction can helpensure that the seal between each filter 12 and the filter head 15 is atleast as effective in preventing particles of a desired size frompassing into the fluid as the filter media 48 inside the particularfilter 12 is at removing particles of that desired size from the fluid.While a pair of grooves 28 is illustrated, it should be appreciated thatthe hub 55 can include any number of grooves as desired that support theinsertion of an O-ring 29.

As illustrated in FIG. 3D, the filter cartridge 42 can be installed intothe housing 40 in an axially downward direction A until the bottom endof the cartridge 42 seats against the bottom of the housing 40. Thecartridge 42 can include a bottom end cap (joined to the shroud 44 inthe manner described above with respect to the upper end cap 51) thatabuts the bottom of the housing 40, or the filter media 48 and/or shroud44 can abut the bottom of the housing. Accordingly, fluid passing intothe void 49 of the post 46 forced to pass through the filter media 48 aswill now be described.

In particular, referring again to FIG. 2, the filter head 15 defines afirst conduit 61 that is in fluid communication with the input end 60 todeliver contaminated fluid to the filter 12 a. The filter head 15further defines a second conduit 63 in fluid communication with the hub55 (see FIG. 3C) to receive filtered fluid from the filter 12 a. Thefirst and second conduits 61 and 63 of the filter head 15 are separatedfrom each other to avoid cross-contamination of input and output fluid.

Referring to FIGS. 2, 3A, and 3C, during operation, the contaminatedfluid flows from the first conduit 61 of the filter head 15 down intothe housing void 50. The end cap 51 can be nonporous to prevent thecontaminated fluid from flowing through the end cap into the filtermedia 48. The outer housing 40 is also nonporous. Accordingly, as fluidpressure amasses in the void 50, the fluid flows radially inward throughthe shroud 44 and filter media 48, and through the post 46. The fluidtravels up through the internal void 49 of the post 46 to the filterhead 15, and subsequently travels downstream in the filtration systemalong the associated conduit 17. In this regard, it should beappreciated that each filter receives “contaminated” fluid and outputsfiltered or “clean” fluid that has a level of contaminating particlesthat is less than the level of contaminating particles present in the“contaminated” fluid. Likewise, the filtration system receives“contaminated” fluid from the industrial process, and outputs “clean”fluid to the industrial process that has a level of particles that isless than the level of particles present in the “contaminated” fluid.When the cartridge 42 is to be removed, the filter housing 40 can beremoved from the filter 12 a in the manner described below, and thecartridge 42 can be pulled out of the housing 40 along the direction ofArrow B of FIG. 3D.

The construction of the filter head 15 and attachment and detachment ofthe filter housing 40 to and from the filter 12 a will now be describedwith reference to FIGS. 4A-B. In particular, the filter head 15 includesan outer circumferential body 70 having a threaded inner surface thatcan mate with a corresponding threaded outer surface of the housing 40,and an inner mounting neck 72 that defines the second conduit 63. Themounting neck 72 includes a lower portion 74 that defines an innersurface 76, and an upper portion 78 that defines an inner surface 80.The mounting neck 72 can be stepped such that the inner surface 76 ofthe lower portion 74 defines a diameter that is greater than that of theinner surface 80 of the upper portion 78. A downward-facingcircumferential seat 82 is thus defined at the interface between theupper portion 78 and the lower portion 80.

In accordance with the illustrated embodiment, the lower portion 74 ofthe mounting neck 72 can include castellation notches 84 disposed at thebottom surface of the lower portion 74. The castellation notches 84prevent an end user from installing a filter cartridge with a flatsmooth gasket instead of a filter cartridge with a double o-ring seal asdepicted in FIG. 3C. For instance, without the castellation notches 84,the lower portion 74 could have a smooth bottom surface which wouldallow an end user to install a filter cartridge with a flat smoothgasket that abuts the bottom surface of the lower portion 74. This wouldcompromise the integrity of the filtration system 10 as a whole becausea flat smooth gasket may not reliably prevent a desired percentage ofparticles of the size trapped by the filter media from infiltrating thesystem 10. In contrast, the double o-ring construction shown in FIG. 3Cis effective at preventing the influx of the size particle trapped bythe filter media. The castellation notches 84 therefore prevent the enduser from having the mistaken belief that the smooth lower portion canform a reliable seal with the flat gasket to keep small particles out ofthe system, as the castellation notches would define visible gapsbetween the bottom surface of the lower portion 73 and the flat gasket.The castellation notches 84 can thus provide an indicator that thefilter head 15 may not provide an adequate seal to such small particleswhen used in a flat gasket arrangement of the type described immediatelyabove. The castellation notches 84 are described in more detail withreference to an adapter as shown an described in U.S. Pat. No.7,320,751, the disclosure which is hereby incorporated by reference asif set forth in its entirety herein.

The O-rings 29 associated with the present filter cartridge 42 areconfigured to seal against the inner surface 76 of the lower portion 74(as opposed to abutting the bottom end of the lower portion 74) therebyproviding a reliable seal with respect to small particles. Because theseal formed between the filter cartridge and the inner surface of theneck 72 effectively seals sub-micron particles from flowing into theoutlet stream without first passing through filter media 48, the filters(and in particular the fourth filter 12 d as described below) areconfigured to remove sub-micron particles from the fluid. In theembodiment illustrated in FIG. 4B, the upper end of the upper end of thehub 55 of the filter cartridge 42 can abut the seat 82 of the filterhead 15 in its installed position such that both O-rings 29 are disposedabove the castellation notches 84, thus sealing both O-rings 29 againstthe inner surface 76. The O-rings 29 can be coated with a lubricant ifdesired, to assist in sliding the filter cartridge 42 in its installedposition. Of course, any number of O-rings 29 can be used to sealagainst the inner surface 76 as desired. Furthermore, the upper end ofthe hub 55 of the filter cartridge 42 need not abut the seat 82 of thefilter head 15 so long as the filter cartridge 42 provides a reliableseal with respect to the neck 72 of the filter head 15.

The first filter can be utilized to provide, for example, a pre-filterthat is rated to remove particles that are at least 7 microns in size.As used herein, a filter that has a particular rating number, forexample 7 microns, means that the filter is capable of removingparticles that are at least the size of the rating number. The filtermedia 48 can be configured such that the first filter 12 a is a 7-micron“catch” filter that can remove large particles (at least 7 microns insize) and absorb oil that may be present in the contaminated fluid.Additionally or alternatively, the first filter 12 a can be specificallydesigned for oil removal, for instance, by incorporating filter mediawith fine denier polypropylene fibers. The first filter 12 a can be arelatively course woven bag filter whose filter media 48 ispolypropylene that can remove relatively large visible “globs” ofmaterial, as well as other particles having a size, for example, of atleast 7 microns. The filter media 48 can be provided as a three-plystructure, or any suitable structure that removes particles from fluidthat passes therethrough.

In an alternative embodiment, the first filter 12 a can be a 5-micronpolyester pleated cartridge. For example, when the fluid that enters thefiltration system 10 from the processing environment 5 does not havesignificant oil particles, and where the particulate load in the fluidis relatively high, using a first filter 12 a that is rated at 5 micronscan provide more effective protection (e.g., extension of usable life)of the second filter 12 b than a 7-micron first filter 12 a.Alternatively still, the first filter 12 a can be configured to removeany size particles as desired by incorporating filter media withdifferent combinations of fiber diameters and by varying the degree ofcalendaring applied to the filter web.

The first filter 12 a can protect or extend the usable life of thesecond filter 12 b by preventing particles having a size of at least 7microns from entering the second filter 12 b and clogging, overwhelming,and/or reducing the useful life of the second filter 12 b. In thisregard, each filter 12 in the filtration system 10 can protect or extendthe usable life of the downstream filters by preventing particles of aspecified size from flowing downstream and entering any of thedownstream filters or industrial system 5. The particle size rating ofthe first filter 12 a, and of the downstream filters in the filtrationsystem 10, can be chosen, for example, to remove a small enough minimumsize particle (e.g., having a largest dimension of at least a specifiedsize, for instance 7 microns), while preventing an excessive drop ofliquid pressure as the liquid passes through the filtration system 10.In addition to absorbing and catching particles, the first filter 12 agenerally adsorbs oils and oil based liquids while allowing water topass through. It will be appreciated that the second and third filters12 b, 12 c, in addition to absorbing and catching particles, may alsoadsorb oils in certain alternative embodiments.

The second filter 12 b can be constructed as described above withrespect to the first filter 12 a, but whose filter media can be madefrom polypropylene configured to remove particles having a largestdimension of at least 0.45-micron. The second filter 12 b can thusremove particles that pass through the first filter 12 a, and thus israted to filter particles having a size that is less than the size ofparticles that are filtered by the first filter 12 a.

The second filter 12 b can alternatively be provided as a 1.0-micronnominally rated, pleated, calendared, micro-fiber polypropylene filter.For example, when the fluid that enters the filtration system 10 fromthe industrial system 5 has a smaller particle size distribution, usinga second filter 12 b that is rated at 1.0 microns can provide a similarlevel of protection of the third filter 12 c as a 0.45-micron secondfilter 12 b, but at a lower cost.

The third filter 12 c can be constructed in the manner described abovewith respect to the first and second filters, but whose filter media canbe made from polypropylene configured to remove particles having alargest dimension of at least 0.2 micron. Hence, during operation thethird filter 12 c removes particles that pass through the second filter12 b, for example, particles having a largest dimension between 0.2 and0.45 micron. Of course, it should be appreciated that the third filter12 c can be constructed to alternatively remove particles having anydesired largest dimension.

The fourth filter 12 d can be provided as a multi-layered percentageremoval nano-filter, or nano-filter, that is capable of removing apercentage of sub-micron size particles including colloids andmicrobiological particles through adsorption, absorption, and catching.For example, the filter media of the fourth filter 12 d can be made fromnanoalumina fibers grafted onto microglass structural fibers.

Referring now to FIG. 5, the fourth filter 12 d can be a multi-layerednano-filter. The nano-filter 12 d can include an outer support cage orshroud 44, an inner support core or post 46, and one or more pleatednano-filter layers 32 comprised of filter media 48 located in thecartridge receptacle 52 that is disposed between the shroud 44 and thepost 46. In use, fluid entering the nano-filter 12 d can flow into thenano-filter 12 d through the plurality of openings 45 of the outershroud 44. The fluid can then pass through the pleated filter layers 32and out of the nano-filter 12 d through the openings 47 of inner post46. The filter media 48 of the pleated filter layers 32 can be made fromDisruptor™ media, for example, that is manufactured by Ahlstrom, Inc.having corporate offices located in Helsinki, Finland. The filter media48 is further described in U.S. Pat. No. 7,601,262, the disclosure ofwhich is hereby incorporated by reference as if set forth in itsentirety herein.

The pleated filter layers 32 can include, for example, a first pleatedfilter layer 32 a, a second pleated filter layer 32 b, and a thirdpleated filter layer 32 c, each successive pleated filter layer 32 beinglocated generally radially inside the previous pleated filter layer 32,wherein all pleated filter layers 32 are oriented substantiallyconcentrically about a common longitudinal axis 37, which defines acentral axis of the post 46. Thus, each successive inner pleated filterlayer can define an outer circumference that is generally being lessthan the outer pleated filter layer, and a number of pleats that isgenerally less than the outer pleated filter layer.

While generally, layer 32 c fits within the inner diameter of layer 32 band layer 32 c fits within the inner diameter of 32 b, it will beappreciated that these layers may overlap in areas 33. Each layer 32 a,32 b, and 32 c comprises a series of outer points 31 a and inner points31 b. These outer points 31 a generally define the outer circumferenceof a layer 32 Inner points 31 b generally define the inner circumferenceof a layer 32. The outer points 31 a may be disposed radially outward orinward of the inner points 31 b of the next outer layer. Furthermore, aportion of the outer points 31 a of a given layer may be disposed * * *radially outward of the inner points 31 b of the next outer layer, and aportion of the outer points 31 a of the given layer may be disposedradially inward of the inner points 31 b of the next outer layer. Forexample, as identified at region 33 a, certain outer points 31 a of themiddle layer 32 b are disposed radially outward of inner points 31 b ofthe outermost layer 32 a. Similarly, as identified at region 33 b,certain outer points 31 a of the innermost layer 32 c are disposedradially outward of the inner points 31 b of middle layer 32 b. In thisregard, regions of the layers 32 a, 32 b, and 32 c may overlap withrespect to a circumferentially extending axis. Alternatively, certainouter points 31 a of the middle layer 32 b are disposed radially inwardof inner points 31 b of the outermost layer 32 a. Similarly, certainouter points 31 a of the innermost layer 32 c are disposed radiallyinward of the inner points 31 b of middle layer 32 b. In this regard,regions of the layers 32 a, 32 b, and 32 c may not overlap each otherwith respect to a circumferentially extending axis. Embodiments mayinclude any number of overlapping regions 33 or may spaced regions. Aportion, up to all, of a given layer may overlap a radially adjacentlayer, while a portion, up to all, of a given layer may be radiallyspaced from a radially adjacent layer.

Referring now to FIG. 5, the three layers of filter media 32 a, 32 b,and 32 c each have different numbers of pleats. The outer layer 32 a hasthe largest number of pleats and inner layer 32 c has the smallestnumber of pleats. The number of pleats in each layer can be determinedat least in part based on the desired number of pleats for the givensurface area of filter media in each layer 32 a, 32 b, and 32 c. Forinstance, an outer layer having a larger circumferential length has morepleats than an inner layer having a smaller circumferential length.Because the pleats of adjacent layers are not pleated together toproduce layers that are fully nested within each other, a gap isdisposed between adjacent layers of filter media. Accordingly, duringoperation, fluid passes from one layer, through the gap, andsubsequently through the adjacent layer, finding its own path throughone of the pores 35 (see FIG. 6) and subsequently enhancing the overallperformance of the filter. It will be appreciated that the pleats of twoor more layers may intersect or otherwise be joined at certain locationswithout affecting the overall performance of the filter, so long as atleast a portion up to all of each layer is spaced from its adjacentlayer so as to define a gap between the layers.

Alternatively, in some embodiments, each of the pleated filter layers 32can be co-pleated in a single pleated orientation. Although threepleated filter layers 32 are shown in FIG. 5, any number of pleatedfilter layers 32 can be used, including 1, 2, 4, 5, 6, 8, 10, or anyother number of pleated filter layers 32 that may be needed to meet theparticular desired performance characteristics of the filtration system10.

Yet another embodiment may comprise filter media 48 that forms a singlefilter layer 32 that is wrapped spirally around post 46 (not shown). Inthis embodiment, filter layer 32 would function similarly to theembodiment depicted in FIG. 5.

The inclusion of three pleated filter layers 32 in the nano-filter 12 dcan be more effective at removing sub-micron size particles than asingle pleated filter layer. For example, each pleated filter layer 32can be made from a percentage removal media (e.g., Disruptor™ media),which means that a particular percentage of sub-micron size particles(e.g., 99.9%) is removed from a liquid as the liquid passes through eachpleated filter layer 32. Therefore, wherein fluid passing through asingle pleated filter layer 32 can include one-thousandth of thesub-micron particles that were previously in the fluid, fluid passingthrough three pleated filter layers 32 in series can includeone-billionth of the sub-micron particles that were previously in thefluid.

Referring now to FIG. 6, each of the pleated filter layers 32 caninclude a web of nanoalumina fibers that have an electrokinetic chargepotential resulting from exposed Al+++ions on the surface of the fibers.Because the nanoalumina fibers in pleated filter layers 32 areelectro-positive, the pleated filter layers 32 can remove negativelycharged microorganisms such as bacteria and viruses, as well asendotoxins. For example, fumed silica particles of approximately 25nanometers in size can be adsorbed and separated from a fluid byelectro-adhesion to the nanoalumina fibers in the pleated filter layers32.

For example, FIG. 6 depicts three microglass fibers 34 included in apleated filter layers 32, each microglass fiber 34 being coated withnanoalumina. The microglass fibers 34 can be dimensioned as desired, forinstance 0.65 microns in width, and can define respective pores 35 thatcan be dimensioned as desired, such as 3 microns long by 2 microns wideas illustrated. Due to the high electrokinetic charge potential of thenanoalumina coated microglass fibers 34, each microglass fiber 34produces a charge field 36 that extends up to 1 micron away from thecenter of the microglass fiber 34 in each direction (e.g., in water andother polar solutions), measured in a direction perpendicular to thelongitudinal axis of each microglass fiber 34. The charge field 36surrounding each microglass fiber 34 can create a nearly total captureof the cross section of the entire volume of the pore 35. This captureis accomplished by the electrokinetic charge potential of thenanoalumina coated microglass fibers 34. In an exemplary embodiment,there can be approximately 400 layers of nanoalumina coated microglassfibers 34 in each approximately 0.8 mm thick pleated filter layer 32. Inan exemplary embodiment, the flow rate of the fluid through the pleatedfilter layers 32 can be set at a predetermined maximum flow rate so thatparticles are not forced through the charge field 36 of the microglassfibers 34 without being retained in the pleated filter layers 32.

While the filtration system 10 has been illustrated and described inconnection with four filters 12 a-d having particular construction andfiltration characteristics (such as particle size ratings), it should beappreciated that the filtration system 10 can include one or more of theabove-described filters in any desired order, and can include greaterthan or less than four filters as desired. For instance, the filtrationsystem can include a single filter provided as the fourth filter 12 ddescribed herein, or a pair of filters including any of the filters 12a-c in combination with the fourth filter 12 d, or three filtersincluding one or more of the filters 12 a-c in combination with thefourth filter 12 d.

In one embodiment, the industrial process 5 can be a printing orlithographic environment. A printing or lithographic environmenttypically includes a fountain solution, which is an aqueous component ina printing or lithographic process that prevents ink from depositing inthe non-image areas and cleans the background areas of the printingplate. Such fountain solutions can become contaminated by the inks beingused. The particles can include various contaminants that need to beremoved, including, for example, solvents, pigments, dyes, resins,lubricants, solubilizers, surfactants, particulate matter, fluorescers,and other materials. Removing these particles from the fountain solutioncan increase the useful life of the fountain solution, reduce the amountof maintenance time spent cleaning the printing or lithographyequipment, and/or reduce the amount of scrap produced by the equipment.In such an environment, the fountain solution can be circulated out of afountain solution storage tank, through the filtration system 10, andback into the storage tank for continued use in the printing orlithographic environment. The filtration system 10 can allow a user tomaintain the quality of a fountain solution without disturbing thechemistry (e.g., maintaining conductivity and pH) of the solution. Forexample, in an exemplary embodiment, the filtration system 10 can beused to clean a fountain solution having a pH of 3.5-9.

The industrial process 5 can be a water filtration system for a dairyfarm, which can filter some or all of the water entering the dairy farm.The use of the filtration system 10 can improve the health of animalsand the quality and quantity of the milk produced. The industrialprocess 5 can be a water filtration system for a pharmaceuticalenvironment or for a drinking water environment. In the dairy farm,pharmaceutical environment, and drinking water environment, thefiltration system 10 can remove endotoxins, bacteria, viruses and/orother contaminants from the water. For example, an embodiment of thefiltration system 10 was able to reduce endotoxins levels in apharmaceutical environment to levels below 0.25 EU/ml, which is themaximum limit for pharmaceutical water for injection quality. In anexemplary embodiment, industrial process 5 can be a reverse osmosissystem for a high end water treatment system.

The industrial process 5 can be an electroplating environment. Forexample the filtration system 10 can be used to remove trace metals inthe discharge fluid from an electroplating process. The filtrationsystem 10 can be used to recover precious metals from the dischargefluid and dispose unwanted trace metals, so that the discharge fluid canbe reused in the electroplating environment.

The embodiments described in connection with the present invention havebeen presented by way of illustration, and the present invention istherefore not intended to be limited to the disclosed embodiments.Accordingly, those skilled in the art will realize that the invention isintended to encompass all modifications and alternative arrangementsincluded within the spirit and scope of the invention, as set forth bythe appended claims.

1. A fluid filtration system configured to remove particles from afluid, the filtration system comprising: a frame; a first filtersupported by the frame, the at least one filter including a filter mediaconfigured to remove particles having a dimension greater than a firstsize; and a nano-filter supported by the frame and disposed downstreamof the first filter with respect to fluid flow, the nano-filter adaptedto remove sub-micron particles from the fluid, the sub-micron particleshaving a largest dimension smaller than the those filtered by the firstfilter, the nano-filter including a plurality of adjacent pleated filterlayers, each pleated filter layer being oriented substantiallyconcentrically about a common longitudinal axis, and at least a portionof each pleated filter layer being spaced from its adjacent pleatedfilter layer.
 2. The filtration system of claim 1, wherein the pluralityof pleated filter layers comprise electro-positive fibers.
 3. Theplurality of pleated filter layers of claim 2 wherein theelectro-positive fibers comprise nanoalumina fibers grafted ontomicroglass structural fibers.
 4. The filtration system of claim 1,wherein at least one of the filters further comprises a filter headhaving a mounting hub and castellations located around the periphery ofthe mounting hub, the filter head coupling the filter to a respectiveconduit that carries the fluid.
 5. The filtration system of claim 1wherein the pleated filter layers each have different numbers of pleats.6. The filtration system of claim 1, wherein the nano-filter comprisesthree pleated filter layers.
 7. The filtration system of claim 1,wherein at least a portion of a select one of the pleated filter layersoverlaps its adjacent filter layer.
 8. The filtration system of claim 7,wherein at least a portion of the select one of the pleated filterlayers does not overlap its adjacent filter layer.
 9. A nano-filtercartridge comprising: an outer support cage; an inner support coredisposed inside the outer support cage so as to define a void disposedbetween the inner support core and the outer support cage; and at leasta first pleated filter layers disposed within the void and a secondpleated filter layer disposed within the void at a location adjacent thefirst pleated filter layer, such that at least a portion of the firstand second filter layers is spaced from each other.
 10. The nano-filtercartridge of claim 9 wherein the first and second pleated filter layersis oriented substantially concentrically about a common longitudinalaxis.
 11. The nano-filter cartridge of claim 10 further comprising athird layer disposed adjacent at least one of the first and secondlayers and oriented substantially concentrically about the commonlongitudinal axis.
 12. The nano-filter cartridge of claim 11 wherein thefirst, second, and third layers comprise respective inner, middle, andouter layers, and the outer layer has more pleats than the inner layer.13. The nano-filter cartridge of claim 9 wherein the filter layerscomprise a plurality of electropositive fibers that define porestherebetween.
 14. The nano-filter cartridge of claim 13 wherein theelectropositive fibers are nanoalumina fibers grafted onto microglassstructural fibers.
 15. The nano-filter cartridge of claim 9 furthercomprising an upper end cap, the upper end cap comprising at least twogrooves adapted to accommodate insertion of respective o-rings.
 16. Amethod of removing submicron particles from a fluid comprising: passingthe fluid through a first filter, wherein the first filter removesparticles that are larger than a first size; and passing the fluidthrough a second filter, wherein the second filter removes particlesthat are smaller than the first size and wherein the second filter is anano-filter having a filter layer that comprises a web ofelectropositive fibers defining fluid receiving pores therebetween. 17.The method of claim 16 further comprising attracting submicron particlesfrom the fluid to the electropositive fibers.